g6pd test

Glucose-6-Phosphate Dehydrogenase (G6PD) is an enzyme involved in energy production. It is found in red blood cells (RBCs) and helps protect them from certain toxic by-products of cellular metabolism. G6PD is involved in the first step of the pentose phosphate pathway which protects cells against oxidative damage. By reducing nicotinamide adenine dinucleotide phosphate (NADP) to nicotinamide adenine dinucleotide phosphate hydrogen (NADPH), G6PD helps the cells to maintain glutathione in its reduced form. This in turn allows glutathione peroxidase to function properly and rid the cells of peroxide. RBCs rely exclusively on the pentose phosphate pathway and therefore G6PD to provide NADPH for this purpose since RBCs lack mitochondria. The rate of G6PD activity is controlled by the concentrations of NADPH and NADP in the cell. When NADPH is oxidized to NADP, G6PD activity increases to replenish NADPH. In G6PD deficiency, erythrocytes are limited in their ability to increase G6PD activity and are, therefore, more vulnerable to oxidative damage.

G6PD deficiency is inherited, passed from parent to child, due to mutations or changes in the G6PD gene that cause decreased enzyme activity. Since men have one X and one Y sex chromosome, their single X chromosome carries the G6PD gene. This may result in a G6PD deficiency if a male inherits the single X chromosome with an altered gene.

Since women have two X sex chromosomes, they inherit two copies of the G6PD gene. Women with only one mutated gene (heterozygous) produce enough G6PD that they usually do not experience any symptoms (i.e., asymptomatic), but under situations of stress, they may demonstrate a mild form of the deficiency.

Glucose-6-phosphate dehydrogenase (G6PD) enzyme testing is used to screen for G6PD deficiencies. A low level of G6PD enzyme indicates a deficiency. An affected person is more likely to experience symptoms when exposed to a trigger.

High-dose ascorbic acid (Vitamin C) promotes the production of hydrogen peroxide as a by-product of its cycling between its ionized form and the ascorbate radical form. Hydrogen peroxide is a potent oxidizer, and increased production results in damage of G6PD-deficient RBCs and ultimately hemolysis (breakdown of RBCs) in patients. The enzyme glutathione peroxidase needs reduced glutathione to help eliminate hydrogen peroxide. As mentioned, the decrease in NADPH decreases the overall storage of reduced glutathione and essentially renders the glutathione peroxidase ineffective.